1. Field of the Invention
The present invention relates to a bonding apparatus, and more particularly, to a substrate bonding apparatus for manufacturing a liquid crystal display device and a method for driving the substrate bonding apparatus.
2. Discussion of the Related Art
In response to an increasing demand for various types of displays devices, flat panel type displays such as liquid crystal display (LCD), plasma display panel (PDP), electro-luminescent display (ELD), and vacuum fluorescent display (VFD) have been developed. In particular, LCD devices have been commonly used because of their high resolution, light weight, thin profile, and low power consumption. In addition, LCD devices have been implemented in mobile devices, such as monitors for notebook computers, and for monitors of computers and televisions. Accordingly, efforts to improve image quality of LCD devices contrast with benefits of their high resolution, light weight, thin profile, and low power consumption. In order to incorporate LCD devices as a general image display, image qualities such as fineness, brightness, large-sized area, for example, must be maintained.
Processes for manufacturing LCD devices according to the related art may be divided into two different categories: liquid crystal injection and liquid crystal dropping. The liquid crystal injection method includes steps of forming a sealant pattern on one of the first and second substrates to form an injection inlet, bonding the first and second substrates to each other within a vacuum processing chamber, and injecting liquid crystal material through the injection inlet. The liquid crystal dropping method, which is disclosed in Japanese Patent. Application No. 11-089612 and 11-172903, includes steps of dropping liquid crystal material on a first substrate, arranging a second substrate over the first substrate, and moving the first and second substrates to join to each other, thereby bonding the first and second substrates to each other.
Compared to the liquid crystal injection method, the liquid crystal dropping method is advantageous in that various process steps, such as forming a liquid crystal material injection inlet, injecting the liquid crystal material, and sealing the injection inlet are unnecessary since the liquid crystal material is predisposed on the first substrate.
FIG. 1 is a cross sectional view of a substrate bonding device prior to a deposition process according to the related art. In FIG. 1, the substrate assembly device includes a frame 10, an upper stage 21, a lower stage 22, a sealant dispenser (not shown), a liquid crystal material dispenser 30, a processing chamber including an upper chamber unit 31 and a lower chamber unit 32, a chamber moving system 40, and a stage moving system 50. The chamber moving system 40 includes a driving motor driven to selectively move the lower chamber unit 32 to a first location where outflow of sealant and dropping of liquid crystal material occur, and a second location where the bonding process is performed. The stage moving system 50 includes another driving motor driven to selectively move the upper stage 21 along a vertical direction perpendicular to the upper and lower stages 21 and 22.
FIG. 2 is a cross sectional view of the substrate bonding device prior to a bonding process according to the related art. In FIG. 2, a process of manufacturing a liquid crystal display device using the substrate assembly device according to the related art includes loading a second substrate 52 onto the upper stage 21 and loading a first substrate 51 onto the lower stage 22, as shown in FIG. 1. Then, the lower chamber unit 32 having the lower stage 22 is moved to a first processing location by the chamber moving system 40 for sealant and liquid crystal material dispensing. Subsequently, the lower chamber unit 32 is moved to a second processing location for substrate bonding by the chamber moving system 40. Thereafter, the upper and lower chamber units 31 and 32 are assembled together by the chamber moving system 40 to form a vacuum tight seal, and a pressure in the chamber is reduced by a vacuum generating system (not shown), as shown in FIG. 2.
Then, the upper stage 21 is moved downward by the stage moving system 50 at the vacuum state to closely fasten the second substrate 52 fixed to the upper stage 21 to the first substrate 51 fixed to the lower stage 22. Furthermore, the process for bonding the respective substrates to each other is carried out through a continuous pressurization, thereby completing the manufacture of the LCD device. Thus, after the bonding of the substrates is completed, the upper and lower chamber units 31 and 32 are separated from each other, and the lower chamber unit 32 is moved to an unloading position by the chamber moving system 40, and the bonded substrates are unloaded.
However, the substrate assembly device according to the related art is problematic. First, the substrate assembly device according the related art fails to provide a subsidiary system for stable loading of the substrates onto the upper and lower stages, or unloading the bonded substrates from the lower stage, thereby increasing the probability that the substrates may be damaged during the loading/unloading process. Specifically, the bonded substrates may partially adhere to an upper surface of the lower stage during the bonding process. Then, the substrate assembly device according the related art unloads the bonded substrates without considering whether the substrates have adhered to the lower stage, thereby creating a high probability that damage to the substrates may occur.
Second, the bonded substrates must be unloaded without droop within a central or circumferential portions of the bonded substrates. However, since the substrate assembly device according to the related art does not consider such the droop, an increase in probability that failure due to warpage of the bonded substrates may occur. Specifically, considering that the size of LCD devices are increasing to meet demand, preventing droop during unloading of the bonded substrates is extremely important and necessary.
Third, direct contact between the substrate and the stage causes static electricity to be generated, which may breakdown inner circuits formed on the substrate. In addition, direct contact between the substrates and the stages lowers production yield.
Fourth, in the substrate assembly device according to the related art, the second substrate is loaded on the lower stage of the lower chamber unit, is transferred into a position of the upper stage by the chamber moving system to be loaded on the upper stage, and the lower chamber unit is again moved to load the first substrate on the lower stage. Accordingly, a high possibility that the substrates may be loaded at incorrect locations exists and thus misalignment may occur during loading thereof, thereby increasing the probability that the substrates may be broken.